1. Field of the Invention
The present invention relates to a microlens array sheet having an improved viewing angle and a manufacturing method thereof. More particularly, the present invention relates to a microlens array sheet manufactured by forming microstructures on a transparent substrate or film, subjecting the microstructures to a chemical mechanical polishing (CMP) process, arraying microlenses on the polished microstructures, and forming a gap-filling film on the resulting structure, and a manufacturing method thereof.
2. Description of the Prior Art
At present, microlenses, which are widely used in microoptical systems, are being applied to optical pickup heads, image sensors and the like, and recently, studies to apply the microlenses to various display systems are actively conducted. In more specific examples where the microlenses are applied to the display system, the microlenses are applied in a rear projection screen to enlarge an image projected from a light source and project it onto a screen, and are applied in LCD panels to improve performance for contrast of pixels.
Among the above examples, a microlens array sheet for application to the rear projection screen will now be described in detail. The projection display system is used to enlarge and project an image projected from a light source onto a screen so as to provide the image to viewers, in which the performance of the rear projection screen is determined by various characteristics, such as gain, viewing angle, contrast, resolution and uniformity. Screen uniformity, an essential factor for viewing a high-quality image, is controllable by a manufacturing process.
FIG. 1 is a cross-sectional view of the prior microlens array sheet for application in the rear projection screen. As shown in FIG. 1, a base 3 for embodying light diffusion is formed on a transparent support substrate or film 1, and microlenses 4 are arrayed on the base 3. On the upper surface of the microlenses, a gap-filling film 5 is formed.
The non-uniformities of height and surface roughness of the base become factors deteriorating the optical quality of the microlens array sheet. The non-uniformity of the base height results in a change in the optical properties of an individual microlens. When a microlens array sheet having this base with non-uniform height is used in a rear projection screen, it will influence the shape and density of black matrices, and when it is used in an optical sheet of an image sensor, it will deteriorate the accuracy of the sensor. Also, the non-uniformity of surface roughness of the base influences microlenses formed on the base, thus making it difficult to manufacture a high-quality screen or image sensor.
As described above, the non-uniformity of the base height or surface roughness, which occurs during the manufacturing of the microlens array sheet, acts as a factor deteriorating the optical performance of the microlens array sheet. Particularly in the case of the rear projection screen, when the height of the base becomes non-uniform, the focal length of an individual microlens will vary, and the shape and density of black matrices formed by self-alignment on microlenses will be influenced.